[Hawkular-dev] [inventory] Reading and querying metric type data type

[Lukas Krejci]

Hi all,

while working on [1] I came across an incosistency in how the data type of a 
metric type (i.e. gauge, availability, counter, ...) are stored and presented.

When you read a metric type using the REST API, you get something like this 
back (some fields ommitted for brevity):

{
  "path" : "/t;tnt/mt;myMetricType",
  "unit" : "NONE",
  "type" : "GAUGE",
  "collectionInterval" : 0,
  "id" : "myMetricType"
}

The metric data type is called "type" here (somewhat confusingly) and contains 
the value in upper case.

If you wanted to filter by it, prior to fix to the above mentioned JIRA, you 
had to:

/traversal/...;propertyName=__metric_data_type;propertyValue=gauge

Notice 2 things:
* the name of the property is different
* the value is in lower case

Now the question is how to bring order to this mess. Because the ideal fix 
will break the format of the data, I'd like to discuss this with the rest of 
the team so that we come to a compromise that will amount to the least amount 
of work for all the inventory clients.

There are 2 obvious problems here:
1) the mismatch between the property name in the JSON output and the property 
name used when querying
2) the mismatch of the letter case in JSON output and queried property value

For 1) I'd like rename BOTH the JSON output and queried property name to 
"metricDataType". We can't "type" because its already taken to mean the type 
of the entity and we can't use "__metric_data_type" because it's inconsistent 
with the rest of the properties.

For 2) I'd like to consolidate on the upper case usage because that's the 
default Jackson serialization of the enum.

Both of these (and especially 1)) can break existing clients.

What would be the path of least resistance for your usecase?

[1] https://issues.jboss.org/browse/HWKINVENT-192

Thanks,

-- 
Lukas Krejci